Rename rendering/render_*.dart to rendering/*.dart

sky/sdk/lib/framework/app.dart

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 import 'dart:sky' as sky;
-import 'rendering/render_box.dart';
-import 'rendering/render_node.dart';
+import 'rendering/box.dart';
+import 'rendering/node.dart';
 import 'scheduler.dart' as scheduler;
 
 class AppView {
 
   AppView(RenderBox root) {
     sky.view.setEventCallback(_handleEvent);
     scheduler.init();
     scheduler.addPersistentFrameCallback(_beginFrame);
 
     _renderView = new RenderView(child: root);
@@ skipping 46 matching lines @@
     }
     dispatchPointerEvent(event, result);
   }
 
   void dispatchPointerEvent(sky.PointerEvent event, HitTestResult result) {
     assert(result != null);
     for (RenderNode node in result.path.reversed)
       node.handlePointer(event);
   }
 }